Hi all Happy New Year, I am not a lover of plywood, but reading it seems a lot are! So maybe I am missing something. Frames in hardwood marine ply? Main bearers in ply lamanated so is it better than hardwood? For 1 easy to cut on a CNC machine. Steve.

The reason marine plywood seems to be the preferred choice for my build and many others here (along with many other non-Glen-L boat builds) are that the designs being built were created from the onset with plywood as the chosen building material, taking advantage of plywoods material properties, to build hulls that can be lighter, stronger, easier to construct and more economical than many other building materials and construction methods (especially in one-off non-production builds).

Taking my build as an example, the powertrain that I'm using for my TNT came out of an 8' long jet ski, built in GRP, that tipped the scales at 842 lbs dry weight, and going into a 12'6" plywood hull that will weight less than 600 lbs complete.

Plywood is not good for everything though. Frames are normally built in solid lumber because solid lumber has greater longitudinal strength than plywood and a lot of fastening into the frames is done into endgrain on the edges, where plywood has poor fastener holding capabilities. There are also times that "composite" structures, such as frames and engine stringers, are built using both solid lumber and plywood laminated together, to create members that are stronger, stiffer and more dimensionally stable than either material by themselves.

If you haven't picked up the Boatbuilding With Plywood book by Glen, I definitely recommend it. It explains a lot about the subject.

Plywood is GENERALLY easier to use. In many ways plywood is stronger than lumber lb for lb. Plywood is more stable due to the multiple thin layers laid cross-grained to each other. Patterning out pieces is also a strong suit of plywood.

However, as Dave said, plywood doesn't have great fastener holding capability into the end-grain which limits it's use as a frame member. Dave pointed out that lumber is stronger longitudinally which also lends to frame members being made out of lumber instead of plywood.

Dave also correctly pointed out that having a lamination of both plywood and lumber makes for a stronger piece. That's why gussets are usually made out of ply.

If I recall, plywood usually has less waste and can be made from younger trees which greatly increases it's efficiency and thus reduces the cost. Also means it's a little more environmentally friendly.

Hi, When I build I am going to build in hard wood, frames and hull with epoxy. I don't want my hull made of plywood! Yes more time consuming and more expensive but it nearer how an old boat was made! Steve.

You can definitely do that too. Obviously a lot of really beautiful boats were built in solid lumber. Just make sure that whatever plans you're looking at building are from a design using solid lumber construction.

I may be wrong, but I believe that there will also be a little more involved with upkeep and maintenance of the hull after it's built?

Hi Dave, Had a look at that web sight nice work!! I would cold mould it with epoxy diagonaly and plank the last layer again beaded with epoxy so not a lot different except no ply wood? Hope this makes sense. I looked at Neals Palm Beach build and saw lots of extra frames, so up scaling say 25% would be doable as plan comes in PDF. I think this could be very interesting build in lots of ways! Steve.

125% upscale. That will be a good size boat at 32.5'.Not sure if you've checked yet, but I would verify that the upscale doesn't create too much open space between batters and frames for fasteners when applying the first layer of planking. Has that size upscale been done on this design before?

Hopefully just upscaling will be more straight forward for you than it has been for my TNT. Of course I had to throw some other mods into the mix and moving the frames around, so it got to the point of completely reengineering the hull (I'm thinking at this point it would almost have been easier to start with a blank sheet of paper on mine...... )